In a two-part paper published in the journal Trends in Genetics, Stanford University researcher Gerald Crabtree suggests that evolution is, in fact, making us dumber — and that human intelligence may have actually peaked before our hunter-gatherer predecessors left Africa.

The reason? Life on the veldt was tough, and prehistoric humans’ genes were constantly subjected to selective pressure in an environment where the species’ survival depended on it. For humans, that meant getting smarter. “The development of our intellectual abilities and the optimization of thousands of intelligence genes probably occurred in relatively non-verbal, dispersed groups of peoples before our ancestors emerged from Africa,” Crabtree said in a news release.

The urbanization that followed the development of agriculture simplified survival by removing some of its challenges, which likely weakened natural selection’s ability to eliminate mutations associated with deficiencies in intelligence. Crabtree estimates that over the last 3,000 years (about 120 generations), humans have sustained at least two mutations that have eroded our intellectual and emotional intelligence.

“A hunter-gatherer who did not correctly conceive a solution to providing food or shelter probably died, along with his or her progeny, whereas a modern Wall Street executive that made a similar conceptual mistake would receive a substantial bonus and be a more attractive mate,” Crabtree wrote in the paper. He also noted that the average Athenian from 1000 B.C. would rank among the smartest and most emotionally stable in today’s society.

Not everybody agrees with Crabtree’s reasoning, however. Steve Jones, a geneticist at University College London, believes there is insufficient data to support his theory. “Never mind the hypothesis, give me the data, and there aren’t any,” Jones told The Independent. “I could just as well argue that mutations have reduced our aggression, our depression and our penis length, but no journal would publish that. Why do they publish this?”

Crabtree does argue that no matter how deteriorated our intellectual abilities may have become over the millennia, advancements in technology will someday render these changes insignificant.

“I think we will know each of the millions of human mutations that can compromise our intellectual function and how each of these mutations interact with each other and other processes as well as environmental influences,” Crabtree said in the release. “At that time, we may be able to magically correct any mutation that has occurred in all cells of any organism at any developmental stage. Thus, the brutish process of natural selection will be unnecessary.”

I wonder if we are actually causing other animals to become smarter. We are, after all, making it much harder for them to survive with our tendency to put buildings or concrete and asphalt over any sufficiently flat surface, not to mention our tendency to pollute the water and air and decimate entire ecosystems hundreds of miles away from where we are. We are putting enormous pressures on other animals. Maybe we won't amount to much in the future, but maybe some super-intelligent squirrel descendants will take our ancestors' place?

But, joking aside, this really does make me sad. Could having children inter-racially help eliminate some of the bad mutations?

If dumber means missing the things that should have been obvious and being woefully lacking in reason... perhaps it's because some people have poor health habits. I'd agree, it's a big factor. This video lists a bit of it: http://www.youtube.com/watch?v=89s1MJmmB4w

Actually, given that farming turned out to be more difficult, requiring many new tools and had many unforeseen consequences (salt in soil from irrigation, diseases and pests attacking long term food stores) that had to be solved, as well as driving the need to keep records of what was stored and sales of surplus, farming should have made us more intelligent, or caused us to develop new forms of intelligence while potentially losing old ones. There are hunter-gatherer cultures where nothing much has changed technologically or in lifestyle for tens of thousands of years, because the ancestors already got it all figured out. Why on earth should people just "doing what their forefathers did" be smarter that people having to adapt to a quickly changing world? (I'll give you the emotional...people trying to cope with constantly changing environments are deeply stressed)

Has this professor gone to study the intelligence and good genes of any of these tribal people? The Bushmen of the Kalahari and the Pygmies (Aka, Baka etc) represent some of the earliest preserved lineages, genetically speaking, and so might be closer to this purported maximally intelligent caveman ancestor...any word on how much smarter they are?

If we've been getting stupider, it's been only in the last few hundred years, not millions.

Expanding on the idea that our brains are evolving to accommodate more complex and abstract thinking; as much I would like to believe this , you have to look at conditions necessary to to survive in environments such as the first world that is to say : very little. Looking at basic social dynamics it appears we will end up with the majority getting 'stupid' but a smaller proportion developing in leaps and bounds intellectually due to their predecessors requirement of a certain level of intelligence or rather type of/ E.G. university.

To which my proposal is artificial Darwinism via the progenitor of social engineering that is self sustaining in ideology.

In response to some comments on the evolution of our intelligence and the selective process pertaining to survival of the fittest, this survival theory would depend of the environment remaining the same. It is certain that many people today wouldn't survive if it weren't for the advancements in science and technology that we (as a species) have made. Whether this implies that we could get dumber at the same time that we're getting smarter at finding the solutions to our survival is a bit of a leap. We may not be as fast on our feet (literally) than we were 2,000 years ago to outrun the wildlife, we may not know how to survive harsh winters or know to avoid eating certain foods to avoid poisoning. Today, we don't need those abilities to survive. This may lead to the atrophy of using some of our "instincts" or senses and not require us to process (or concern ourselves with) some intellectual processes needed for our survival. However, this has nothing to do with how we process other information, and everything with what we need to know. Our circumstances for survival have changed. Furthermore, I would suggest that our abilities in abstract thinking have significantly improved and that would support we are getting smarter. Just look at some of the scientific and mathematical equations 8th graders are able to solve, or how kindergartners manipulate a PC or a smart phone. Continuously training our brains to think in multiple dimensions would imply we are learning to use our brains differently and we are able to comprehend and mentally manipulate more complex systems and ideas. While we are getting smarter about certain things, and our brains are continuously being challenged at more complex tasks, we are getting dumber at others. Our vision of the world and our comprehension of our place in society is skewed, leading us to ignore factors that may be required to sustain our survival in generations ahead. The damage we are doing to our planet (because of our intelligence to plunder it of its riches) and the hatred we show one another may well cause our demise, someday. Perhaps, though, that will bring along its built-in solution and in some not so distant future, we may cause a war or a global pandemic that will cause devastating loss of life. Perhaps, in all of these discussions, we should concern ourselves with boosting our 'Emotional Intelligence' and resolve the issues pertaining to our cohabiting on this planet so as to sustain the long term survival of humanity.Cheers, XV

To answer Steve Jones' question: because it's an interesting hypothesis.

A couple of thoughts I have on this:

1.We have a great deal of knowledge today on how natural selection works. It's fairly easy to see that there is little to no selection for intelligence happening in today's human environment. Even when individuals become successful and essentially out compete their peers because of superior intelligence that does not translate into survival or greater reproduction. Because of this it seems we have every reason to expect that under the current environment intelligence will diminish; even if we have no evidence that this has in fact occurred.

2. The lack of selection I'm talking about above is only true for abstract intelligence. We think of our environment as being easily survived compared to life on the Savannah but that is only partly because it suits us and largely because we are adapted to it. Take a hunter gatherer from 10,000 BC and dump him in present day Los Angeles; with no guidance his odds of survival start to look pretty slim. Just look to the infamous "Darwin Awards" for inspiration on the thousands of ways stupidity can kill you(or geld you) in the modern world. I suppose it does take a certain amount of intelligence to understand that replacing an electrical fuse with .22 caliber ammunition is a bad idea. Traffic accidents are the number one cause of violent death in the U.S. so if nothing else there is at least a fair amount of environmental pressure to become a better driver - reaction, coordination, spatial reasoning, planning.

3.We broadly define intelligence as the ability to assimilate and utilize information. But this is a definition that can be used to make even the brightest human appear less intelligent than a chimp or even a dog in certain situations. Chimps are thought to have super-human working memory and subitizing ability. Ayuma the chimp is better at a working memory game than any human, even with equal training. The point is that there is much confusion about what intelligence means because we define it broadly but we measure it - by necessity - very narrowly. The original purpose of the brain is simply to conduct the body's physical movements. Therefore all intelligence however abstract is exapted from this purpose. And therefore it is also reasonable to expect that an adaptation toward increased intelligence in one area might effect a decrease in another.

The Flyn effect seems to directly contradict Crabtree's hypothesis. But I would argue that because of our chronic conflation of many specific measures of intelligence with our extremely broad definition of general intelligence, we could find evidence that humans are both getting smarter and getting "dumber" simultaneously.

"Human beings are getting dumber"...around the world or here in the U.S.? Thanks to the teacher's union and decades of absurd dallying with teaching "techniques" and curriculum, it is clear the U.S. is getting dumber in total numbers. Certainly, we will always have extremely bright, motivated students who become productive adults, but, our last election is empirical evidence that the "DUMBING DOWN OF AMERICA" has been successfully accomplished by the predominant number of teachers. FYI: the phrase "Dumbing Down of America" was coined by none other than a respected democrat, the late N.Y. U.S. Senator Daniel "Patrick" Moynihan.

Also, the late attorney for the UNITED FEDERATION FOR TEACHERS for over 20 years said at a convention:

Who cares what some geneticist "suggests"? It's an argument from authority. The *evidence* is to the contrary, in the form of the Flynn effect ... IQ tests have to keep being recalibrated because the average score keeps rising.

Crabtrees argument that humanity is about to become the Eloi is as valid as measuring IQ by counting the bumps on a person's head.

His argument about the evolutionary biological loss of intellect totally ignores the evolutionary cultural gain in intellect.

Despite his comments about the "intellect" of an Athenian in 1000 BCE, the time period was shortly after the demise of Socrates, the World's First Certified Dyslexic, who viewed reading and writing to be an abomination mostly from his disability to master it. Without the heresy and disobedience of his student Plato, we would never know of the bigoted "wisdom" of Socrates.

Instead our survival as individuals and as a species has gone from the Age of Information (Orwell's "Information is Power") to the Age of Information Overload in which our survival as individuals and as a species is dependent on filtering OUT the specious data that consumes and wastes our time. (You can read about it in your local newspaper, if you can find one.)

And comparing Sumerian letter writing to Native Americans pictographs is specious, since 90% of Native Americans likely have dyslexia and and are still not able to master the flexibility of letter-based writing systems. That too will change with the upcoming advent of lenses that eliminate the chromatic-induced photoreceptor problems that likely cause dyslexia symptoms.

the argument could also go the other way around that intelligence has simply changed from the natural adaptive, to technological abstract, in the last 100 years there has been more abstract advancement of knowledge than in the actual natural arena. there is probably more evidence that the adaptation is towards ever more organized social structures rather than brute survival.

Since they could not invent a non - warring, non - exploitative, non - unequal, non - discriminating, 'without borders' world how long they would be called smart? And yes, they are killing their own environment in which they want to survive. What else is dumbness?

Is the writer of this article aware of the Multiple Intelligences Theory proposed by Howard Gardner?

In his writings, Gardner expressed that each of us are intelligent in different ways. Some of us learn better through reading, others through viewing pictures, others through engaging in physical activities (i.e. hunter-gatherers), etc..

Just because today's human beings do not excel at hunter-gatherer type behaviors DOES NOT mean that "we as a whole are getting dumber." It's amazing that JuJu Kim (the article's writer) did not catch that over-generalization as he was typing this piece.

Articles like this would not, "have gone to press" (to borrow an old phrase) even 10 years ago.

One of the factors that I think dumbs down the population is that at the current time we have very few real challenges. Everything is either mechanized, or electronic, or given to us by the government. The general population just has it too easy.

If we had to struggle to even survive, the dumb ones wouldn't, and if intelligence has a genetic component, the average intelligence of the population would go up

"Recent polls have shown a fifth of Americans can't locate the U.S. on a world map. Why do you think this is?"

"I personally believe that U.S. Americans are unable to do so because, uh, some people out there in our nation don't have maps and, uh, I believe that our education like such as in South Africa and, uh, the Iraq, everywhere like such as, and, I believe that they should, our education over HERE in the U.S. should help the U.S., uh, or, uh, should help South Africa and should help the Iraq and the Asian countries, so we will be able to build up our future, for our children." - Caitlin Upton (2007 Miss Teen USA pageant)

I don't know about anybody else, but this particular human isn't too bright.

wrong in the USA alone the average IQ has fallen 20 base points in the last 70 years intergration caused most of this, we have fallen fron 3th in inteligence to 19 on a worlds ranking in the last 70 years

@John I agree but if North Korea would launch a EMP nuke at the USA then you will find the collage educated would probably not survive, these people have no clue to hard work or the process to even find clean water in a natural environment and water would be the most important aspect to survival, a human can only last 3 days with out water.

With 120 cases of STD's in america the life style these people lead would surly guarantee there demise.

@John We have very few real challenges? I would say the contrary is true. More challenges than ever before, actually. Perhaps on a day to day urban basis we have fewer (needless) decisions to make due to tecnology, but this tecnology is responsible for uncountable other problems from A to Z that we haven't learned to deal with and is putting a validation date on "life as we know it" on the planet. I guess we better get smart quick (or else).

@RobertMiller1 P.S. Learn some grammar and punctuation. If anyone is pulling down the U.S. average intelligence (not IQ -- the average IQ is 100 because it's calibrated that way; duh) it's your stock, whatever that is.

First, thank you for replying to my comment. A couple of additional comments in response:

1) From a review of the literature, I agree that Multiple Intelligence Theory has received some criticism from those in the field. However, that criticism has focused on the statistical applications (regarding the variable, "g"), and not the more qualitative aspects of the theory (i.e. "Are you a visual-learner, or a book-learner?")

2) From a personal anecdotal perspective, I was trained to be a Secondary Education Teacher, and earned my certification in 2010 (in Social Studies, and then English in 2011). In my training, we were exposed to Howard Gardner's Theory on Multiple Intelligence. As a teacher, I also encountered other colleagues who learned the theory in their training as well. Furthermore, to exhibit how the theory has held up over time, my grandmother (a former special education teacher with 25 years experience, who retired in the early 1990s) was well-versed in the theory as well.

In summary, the point of sharing that perspective was to show that (while the theory has been subjected to criticism) the theory can be used in practical, qualitative applications in both psychology and education.

Ah . Well it does actually require a little extra brain power to understand the comment, and it's associated connection with the article. I'm sorry you failed to do so. Perhaps you might reconsider your reading level: "Run Spot Run" is perfect for children.

This illiterate can't even spell "you're". Then he cites a paper that not only doesn't support his claims but has no evidence behind it. As I said, if anyone is bringing down the average IQ, it's him and his kin. Nothing more needs to be said.

The larger the human population grows, the average human I. Q seems to drop. Now how is this possible? Studies show that since the nineteen fifties the average I. Q has dropped a total of three points. This is alarming and confusing at the same time. How with all of our medical and technological advancements is this occurring? Many charts that I have found showed that the average I. Q was at its peak in nineteen fifty that was sixty years ago. Many blame this fall of global I. Q on the fall of the Soviet Union. In the soviet unions control of Eastern Europe, their children were forced to be schooled in far more advanced subjects than modern students. It was a race to attempt to beat the west technologically. In turn the west also made their students study harder and learn more thusly making the average I. Q greatly superior than it had been for many years. Without this compaction the schooling that was installed in a time of panic was called off. Recent studies show that the is now Falling at a rapid rate. The average I.Q. for 2011 is calculated to be 88.54 this is the lowest I.Q. rate in years.

I included literature on educational psychology, general psychology, and teaching pedagogy (from beginner to advanced). Increasingly, the Education profession is delving into psychology for insights into ways students learn, think, and remember/retain information.

My peers and I was certainly given a broad background during my teacher training, and I have no doubt that the upcoming teacher candidates are receiving similar training as well. In fact, in Pennsylvania, all teacher candidates - whether elementary or secondary - must complete 12 credits of special education (as disabled students are increasingly being mainstreamed into regular education classrooms).

I did not include research on cognitive science, because "scientific training" was never a part of my training. However, I could see the false dichotomy in the "book learner v. visual learner." You're right - pictures within the text help to paint a clearer picture for learners and readers alike (especially in 300-page tomes).

My using of Multiple Intelligence Theory as an example was driven by the article's odd question of, "were we getting dumber." Admittedly, the theory isn't perfect, but (to me) it seems that using a mix of those intelligences have helped us to become more efficient "hunter-gatherers," and have therefore helped human beings endure. Change is a constant, and we seem to be pretty good at it.

@mrbomb13@epitygxanwn How wide was your "review of the literature"? Did you include the literature on cognitive science, or were you looking just at education?

It is, after all, the results of cognitive science that suggest your "book learner vs. visual learner" is a false dichotomy: books teach far more effectively for ALL learners when they use visualization techniques well. The days are long over when a scholar like Hermann Weyl could publish a 300 page book claiming to teach a topic with only 3 figures;)

@JimBalter You have lost your argument and have nothing left to cling to but lame name calling. You have lied and you have continued this thread after saying that you would not. You make erroneous statements of things of which you cannot possibly know. You demonstrate with every word that you are a venomous and hateful person. You sir, are the evidence that dump people can pretend to be intelligent but their bluff will sooner or later be called - and I have called you for what you are. A twisted lonely little rain man with nothing in life but self sorrow and forum flaming.

@JimBalter@BarryNeilson So let me get this right. After categoricially stating that you'd say no more to or of me, here you are, three months later, continuing to troll and make delusional abuses. You need to get over my initial tongue-in-cheek posting, and you need to get over yourself. It is possible to be bright without being a complete self-absorbed tool - I suggest you learn how.

@BarryNeilson One more comment ... your tu quoque fallacy further confirms what I wrote of you. Your statements were not made in retaliation for anything, that's an after-the-fact rationalization by a pathetic coward. You started this with your "pointed comment" that "this particular human isn't too bright". It remains a simple fact, apparently beyond your comprehension, that anecdotes are irrelevant to statistical distributions.

@BarryNeilson The point was the irrelevance of anecdotes about one unintelligent person to this article, about statistical distributions of intelligence. Rather than address the substance, you attacked my brain power and my reading ability, and now absurdly take my factual counter to those silly ad hominems as narcissism and attack my interpersonal ability and say I'm a child. You not only confirm my original statement about not being bright, but you also demonstrate that you are an immature and dishonest person. The web, and the planet, is full of such tedious boring garbage as you ... which is the last I will say to or of you.

An IQ of 170 says you. The internet abounds with egotists of no interpersonal ability. However, I will see your narcisistic bluff and raise you one engorged ego. Plus, you can keep your Dunning-Kruger effect; children with high IQ's are still children.